《STL源码剖析》笔记-hash_set、hash_map

上一篇：《STL源码剖析》笔记-hashtable

hash_set

hash_set底层机制由hashtable提供，和set一样能够快速搜索元素，但是set元素插入后会自动排序，而hash_set是无序的。

template <class Value, class HashFcn = hash<Value>,
    class EqualKey = equal_to<Value>,
    class Alloc = alloc>
    class hash_set
{
private:
    // 底层为hashtable
    typedef hashtable<Value, Value, HashFcn, identity<Value>, EqualKey, Alloc> ht;
    ht rep;

public:
    typedef typename ht::key_type key_type;
    typedef typename ht::value_type value_type;
    typedef typename ht::hasher hasher;
    typedef typename ht::key_equal key_equal;

    typedef typename ht::size_type size_type;
    typedef typename ht::difference_type difference_type;
    typedef typename ht::const_pointer pointer;
    typedef typename ht::const_pointer const_pointer;
    typedef typename ht::const_reference reference;
    typedef typename ht::const_reference const_reference;

    typedef typename ht::const_iterator iterator;
    typedef typename ht::const_iterator const_iterator;

    hasher hash_funct() const { return rep.hash_funct(); }
    key_equal key_eq() const { return rep.key_eq(); }

public:
    // 默认构造100大小的hashtable，将会被调整为大于100的预定义质数
    hash_set() : rep(100, hasher(), key_equal()) {}
    explicit hash_set(size_type n) : rep(n, hasher(), key_equal()) {}
    hash_set(size_type n, const hasher& hf) : rep(n, hf, key_equal()) {}
    hash_set(size_type n, const hasher& hf, const key_equal& eql)
        : rep(n, hf, eql) {}

    // 所有的插入操作都是insert_unique，不允许键值重复
    template <class InputIterator>
    hash_set(InputIterator f, InputIterator l)
        : rep(100, hasher(), key_equal()) {
        rep.insert_unique(f, l);
    }
    template <class InputIterator>
    hash_set(InputIterator f, InputIterator l, size_type n)
        : rep(n, hasher(), key_equal()) {
        rep.insert_unique(f, l);
    }
    template <class InputIterator>
    hash_set(InputIterator f, InputIterator l, size_type n,
        const hasher& hf)
        : rep(n, hf, key_equal()) {
        rep.insert_unique(f, l);
    }
    template <class InputIterator>
    hash_set(InputIterator f, InputIterator l, size_type n,
        const hasher& hf, const key_equal& eql)
        : rep(n, hf, eql) {
        rep.insert_unique(f, l);
    }

public:
    // 所有操作几乎都是直接调用hashtable的接口
    size_type size() const { return rep.size(); }
    size_type max_size() const { return rep.max_size(); }
    bool empty() const { return rep.empty(); }
    void swap(hash_set& hs) { rep.swap(hs.rep); }
    friend bool operator== __STL_NULL_TMPL_ARGS(const hash_set&,
        const hash_set&);

    iterator begin() const { return rep.begin(); }
    iterator end() const { return rep.end(); }

public:
    pair<iterator, bool> insert(const value_type& obj)
    {
        pair<typename ht::iterator, bool> p = rep.insert_unique(obj);
        return pair<iterator, bool>(p.first, p.second);
    }
#ifdef __STL_MEMBER_TEMPLATES
    template <class InputIterator>
    void insert(InputIterator f, InputIterator l) { rep.insert_unique(f, l); }
#else
    void insert(const value_type* f, const value_type* l) {
        rep.insert_unique(f, l);
    }
    void insert(const_iterator f, const_iterator l) { rep.insert_unique(f, l); }
#endif /*__STL_MEMBER_TEMPLATES */
    pair<iterator, bool> insert_noresize(const value_type& obj)
    {
        pair<typename ht::iterator, bool> p = rep.insert_unique_noresize(obj);
        return pair<iterator, bool>(p.first, p.second);
    }

    iterator find(const key_type& key) const { return rep.find(key); }

    size_type count(const key_type& key) const { return rep.count(key); }

    pair<iterator, iterator> equal_range(const key_type& key) const
    {
        return rep.equal_range(key);
    }

    size_type erase(const key_type& key) { return rep.erase(key); }
    void erase(iterator it) { rep.erase(it); }
    void erase(iterator f, iterator l) { rep.erase(f, l); }
    void clear() { rep.clear(); }

public:
    void resize(size_type hint) { rep.resize(hint); }
    size_type bucket_count() const { return rep.bucket_count(); }
    size_type max_bucket_count() const { return rep.max_bucket_count(); }
    size_type elems_in_bucket(size_type n) const
    {
        return rep.elems_in_bucket(n);
    }
};

hash_map
hash_map底层机制由hashtable提供，和map一样能够快速搜索元素，但是map元素插入后会自动排序，而hash_map是无序的。

template <class Key, class T, class HashFcn = hash<Key>,
    class EqualKey = equal_to<Key>,
    class Alloc = alloc>
    class hash_map
{
private:
    // 底层为hashtable
    typedef hashtable<pair<const Key, T>, Key, HashFcn, select1st<pair<const Key, T> >, EqualKey, Alloc> ht;
    ht rep;

public:
    typedef typename ht::key_type key_type;
    typedef T data_type;
    typedef T mapped_type;
    typedef typename ht::value_type value_type;
    typedef typename ht::hasher hasher;
    typedef typename ht::key_equal key_equal;

    typedef typename ht::size_type size_type;
    typedef typename ht::difference_type difference_type;
    typedef typename ht::pointer pointer;
    typedef typename ht::const_pointer const_pointer;
    typedef typename ht::reference reference;
    typedef typename ht::const_reference const_reference;

    typedef typename ht::iterator iterator;
    typedef typename ht::const_iterator const_iterator;

    hasher hash_funct() const { return rep.hash_funct(); }
    key_equal key_eq() const { return rep.key_eq(); }

public:
    // 默认构造100大小的hashtable，将会被调整为大于100的预定义质数
    hash_map() : rep(100, hasher(), key_equal()) {}
    explicit hash_map(size_type n) : rep(n, hasher(), key_equal()) {}
    hash_map(size_type n, const hasher& hf) : rep(n, hf, key_equal()) {}
    hash_map(size_type n, const hasher& hf, const key_equal& eql)
        : rep(n, hf, eql) {}
        
    // 所有的插入操作都是insert_unique，不允许键值重复
    template <class InputIterator>
    hash_map(InputIterator f, InputIterator l)
        : rep(100, hasher(), key_equal()) {
        rep.insert_unique(f, l);
    }
    template <class InputIterator>
    hash_map(InputIterator f, InputIterator l, size_type n)
        : rep(n, hasher(), key_equal()) {
        rep.insert_unique(f, l);
    }
    template <class InputIterator>
    hash_map(InputIterator f, InputIterator l, size_type n,
        const hasher& hf)
        : rep(n, hf, key_equal()) {
        rep.insert_unique(f, l);
    }
    template <class InputIterator>
    hash_map(InputIterator f, InputIterator l, size_type n,
        const hasher& hf, const key_equal& eql)
        : rep(n, hf, eql) {
        rep.insert_unique(f, l);
    }

public:
    size_type size() const { return rep.size(); }
    size_type max_size() const { return rep.max_size(); }
    bool empty() const { return rep.empty(); }
    void swap(hash_map& hs) { rep.swap(hs.rep); }
    friend bool
        operator== __STL_NULL_TMPL_ARGS(const hash_map&, const hash_map&);

    iterator begin() { return rep.begin(); }
    iterator end() { return rep.end(); }
    const_iterator begin() const { return rep.begin(); }
    const_iterator end() const { return rep.end(); }

public:
    pair<iterator, bool> insert(const value_type& obj)
    {
        return rep.insert_unique(obj);
    }
#ifdef __STL_MEMBER_TEMPLATES
    template <class InputIterator>
    void insert(InputIterator f, InputIterator l) { rep.insert_unique(f, l); }
#else
    void insert(const value_type* f, const value_type* l) {
        rep.insert_unique(f, l);
    }
    void insert(const_iterator f, const_iterator l) { rep.insert_unique(f, l); }
#endif /*__STL_MEMBER_TEMPLATES */
    pair<iterator, bool> insert_noresize(const value_type& obj)
    {
        return rep.insert_unique_noresize(obj);
    }

    iterator find(const key_type& key) { return rep.find(key); }
    const_iterator find(const key_type& key) const { return rep.find(key); }

    T& operator[](const key_type& key) {
        return rep.find_or_insert(value_type(key, T())).second;
    }

    size_type count(const key_type& key) const { return rep.count(key); }

    pair<iterator, iterator> equal_range(const key_type& key)
    {
        return rep.equal_range(key);
    }
    pair<const_iterator, const_iterator> equal_range(const key_type& key) const
    {
        return rep.equal_range(key);
    }

    size_type erase(const key_type& key) { return rep.erase(key); }
    void erase(iterator it) { rep.erase(it); }
    void erase(iterator f, iterator l) { rep.erase(f, l); }
    void clear() { rep.clear(); }

public:
    void resize(size_type hint) { rep.resize(hint); }
    size_type bucket_count() const { return rep.bucket_count(); }
    size_type max_bucket_count() const { return rep.max_bucket_count(); }
    size_type elems_in_bucket(size_type n) const
    {
        return rep.elems_in_bucket(n);
    }
};

C++11中对应的容器

hash_set和hash_map不属于STL标准，所以一般情况下无法使用，不过C++11中有对应的容器unordered_set和unordered_map。

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